Bookmobiles, in use in the United States since 1905, are just one form of mobile delivery of library services. The former IFLA Mobile Libraries Section, now part of the Public Libraries Section, investigated delivery services around the world. In a survey conducted in in 1999-2001 they offered the following options for delivery: Bicycle, Wagon, Donkey Cart, Camel, Motorbike, Boat, Helicopter, Train, and the more usual bookmobiles in the form of special trucks, vans or mini-buses.

Mates, Barbara T. "AccessAbility @ Cleveland Public Library." Public Libraries Vol. 42, No. 1 (January/February 2003): 28-31.Entire issue available online as an Adobe Reader PDF file; see page 32 of the 68-page PDF file.
The third page of the article features a photo of the Cleveland Public Library's "mobile services unit," or bookmobile, which is nicknamed "Bessie." There's also a section on that page, titled, "The People's University on Wheels," which explains that "Bessie" has "a wheelchair lift and is outfitted with adaptive technology software and CCTV. Facilities routinely visited include children's residential rehabilitation, senior citizen, and rehabilitation facilities."

"Service on Wheels." Library Journal March 15, 2006 (Vol. 131; Movers & Shakers Supplement, page 28).
Brief portrait of Jeannie Dilger-Hill, explaining that what she "loves most about being outreach services manager at King County Library System (KCLS) is that the eight vehicles in her charge visit 130 nursing homes, senior centers, low-income housing developments, child care centers, rehabilitation centers, and hospitals, providing fair and equal access to the information upon which a democratic society depends."

Tower, Mary. "Seniors and Mobile Library Services." Bookmobile and Outreach Services Vol. 3, No. 2 (2000): 37-42.
The article speaks extensively on pages 40-41 about both the advantages and the drawbacks to equipping a bookmobile with a wheelchair lift, advising that even though "a wheelchair lift is not required by the ADA, if you already have senior patrons using wheelchairs at nursing homes or if you go to other sites frequented by wheel chair users, or expect to do so in the future, then the need for a wheel chair lift may well outweigh the drawbacks. It is your local situation, your service program that must determine your choice, not the decision another library has made, even one in an adjacent jurisdiction."